The isle of Askel faces more of the brunt of the northern storms than any of the other isles. Hrafnel's mountains are deep enough to break up the harsh winds and climate, but Askel's mountains do not shelter the rest of the island very well. As a result, the weather is typically harsher on Askel, but the people are hardier.
Unulf is a smaller island that is considered to be a part of the Kingdom of Askel, it's position and isolation from the larger island does lend it a bit of its own individuality. Unulf is inhabited mostly by Northlanders. However, the island is much more sparse in timber than the other islands, so there are fewer ships being crafted on the island. Instead, the hills and small mountains are mined for resources.